GaN based Light-Emitting Diode as 21 st century's new-type light-emitting devices for solid state lighting shows a series of advantages just as following: small, electricity-saving, with long service life, free of the polluted-environment Hydrargyrum, efficient and low maintenance and with which GaN based Light-Emitting Diode can be widely used in a variety of lighting facility which including interior illumination, traffic lights, automobile tail light/headlamp, outdoor large screen, display and advertising screen. The trend that replacing currently used all kinds of light bulbs and fluorescent lamps had already emerged. And the new type of green lighting source will have become the new generation of illuminating system, which will have introduced a profound effect on energy-conserving, environment-protection and the improvement of life quality. The fabrication techniques of White LED are as following: the three-monochrome blue-green-and-red LED combination, blue LED mixed with yellow fluorescent powder, ultraviolet LED mixed with red -green-and-blue fluorescent powder. However, there is little inorganic luminescent material which can be excited by blue LED. The mostly used fluorescent materials Yttrium Aluminitum Garnet (YAG) and Ce so far combined with blue LED on basis of the principle of complementary color, white light reached. However, the photochromism of the light provided by YAG closes to yellow-green, high-color-temperature cool coloured white light can only be reached with color rendering index low. Then, red fluorescent powder should be considered for different color-temperature white light ranged from cool colors to warm colors, and also for better color rendering index.
The currently used green fluorescent powder, which can be excited by blue light (420-480 nm), blended mostly with divalent Europium Sulfide, such as (Ca, Sr, Ba)S: Eu2+. However, with poor chemical resistance and thermal stability, Sulfide fluorescent powder is phone to react with the moisture from the air, the heat after decomposition, and with some exhaust fumes released in manufacture procedure which polluted the air. Recently, the using nitrogen compounds, which composed by SiN4 as the basic unit, as the host material for the fluorescent powder received great attention. On the basis of the strong covalent bond and the large crystal field splitting, when mixed with lanthanon such as divalent Europium, these compounds can excite luminescence under the longer wavelengths, such M2Si5N8: Eu2+ (M=Sr, Ca, Ba) which can emit red light. However, even with high quantum efficiency, the nitride red fluorescent powder has high luminescence decay, which severely limits its applications.